/* Extended Module Player
 * Copyright (C) 1996-2024 Claudio Matsuoka and Hipolito Carraro Jr
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

/*
 * Sun, 31 May 1998 17:50:02 -0600
 * Reported by ToyKeeper <scriven@CS.ColoState.EDU>:
 * For loop-prevention, I know a way to do it which lets most songs play
 * fine once through even if they have backward-jumps. Just keep a small
 * array (256 bytes, or even bits) of flags, each entry determining if a
 * pattern in the song order has been played. If you get to an entry which
 * is already non-zero, skip to the next song (assuming looping is off).
 */

/*
 * Tue, 6 Oct 1998 21:23:17 +0200 (CEST)
 * Reported by John v/d Kamp <blade_@dds.nl>:
 * scan.c was hanging when it jumps to an invalid restart value.
 * (Fixed by hipolito)
 */


#include "common.h"
#include "effects.h"
#include "player.h"
#include "mixer.h"

#ifndef LIBXMP_CORE_PLAYER
#include "far_extras.h"
#endif

#define VBLANK_TIME_THRESHOLD	480000 /* 8 minutes */

#define S3M_END		0xff
#define S3M_SKIP	0xfe


static int scan_module(struct context_data *ctx, int ep, int chain)
{
    struct player_data *p = &ctx->p;
    struct module_data *m = &ctx->m;
    const struct xmp_module *mod = &m->mod;
    const struct xmp_track *tracks[XMP_MAX_CHANNELS];
    const struct xmp_event *event;
    int parm, gvol_memory, f1, f2, p1, p2, ord, ord2;
    int row, last_row, break_row, row_count, row_count_total;
    int orders_since_last_valid, any_valid;
    int gvl, bpm, speed, base_time, chn;
    int frame_count;
    double time, start_time, time_calc;
    int inside_loop, line_jump;
    int pdelay = 0;
    struct flow_control f;
    struct pattern_loop loop[XMP_MAX_CHANNELS];
    int i, pat;
    int has_marker;
    struct ord_data *info;
#ifndef LIBXMP_CORE_PLAYER
    int st26_speed;
    int far_tempo_coarse, far_tempo_fine, far_tempo_mode;
#endif
    /* was 255, but Global trash goes to 318.
     * Higher limit for MEDs, defiance.crybaby.5 has blocks with 2048+ rows. */
    const int row_limit = IS_PLAYER_MODE_MED() ? 3200 : 512;

    if (mod->len == 0)
	return 0;

    for (i = 0; i < mod->len; i++) {
	pat = mod->xxo[i];
	memset(m->scan_cnt[i], 0, pat >= mod->pat ? 1 :
			mod->xxp[pat]->rows ? mod->xxp[pat]->rows : 1);
    }

    /* Use a temporary flow_control so the scan can borrow the player's
     * Pattern Loop handler. */
    memset(&f, 0, sizeof(f));
    f.loop = loop;
    for (i = 0; i < mod->chn; i++) {
	loop[i].start = 0;
	loop[i].count = 0;
    }
    f.loop_dest = -1;
    f.loop_param = -1;
    f.loop_start = -1;
    f.loop_count = 0;
    f.loop_active_num = 0;
    line_jump = 0;

    gvl = mod->gvl;
    bpm = mod->bpm;

    speed = mod->spd;
    base_time = m->rrate;
#ifndef LIBXMP_CORE_PLAYER
    st26_speed = 0;
    far_tempo_coarse = 4;
    far_tempo_fine = 0;
    far_tempo_mode = 1;

    if (HAS_FAR_MODULE_EXTRAS(ctx->m)) {
	far_tempo_coarse = FAR_MODULE_EXTRAS(ctx->m)->coarse_tempo;
	libxmp_far_translate_tempo(far_tempo_mode, 0, far_tempo_coarse,
				   &far_tempo_fine, &speed, &bpm);
    }
#endif

    has_marker = HAS_QUIRK(QUIRK_MARKER);

    /* By erlk ozlr <erlk.ozlr@gmail.com>
     *
     * xmp doesn't handle really properly the "start" option (-s for the
     * command-line) for DeusEx's .umx files. These .umx files contain
     * several loop "tracks" that never join together. That's how they put
     * multiple musics on each level with a file per level. Each "track"
     * starts at the same order in all files. The problem is that xmp starts
     * decoding the module at order 0 and not at the order specified with
     * the start option. If we have a module that does "0 -> 2 -> 0 -> ...",
     * we cannot play order 1, even with the supposed right option.
     *
     * was: ord2 = ord = -1;
     *
     * CM: Fixed by using different "sequences" for each loop or subsong.
     *     Each sequence has its entry point. Sequences don't overlap.
     */
    ord2 = -1;
    ord = ep - 1;

    gvol_memory = break_row = row_count = row_count_total = frame_count = 0;
    orders_since_last_valid = any_valid = 0;
    start_time = time = 0.0;
    inside_loop = 0;

    while (42) {
	/* Sanity check to prevent getting stuck due to broken patterns. */
	if (orders_since_last_valid > 512) {
	    D_(D_CRIT "orders_since_last_valid = %d @ ord %d; ending scan", orders_since_last_valid, ord);
	    break;
	}
	orders_since_last_valid++;

	if ((uint32)++ord >= mod->len) {
	    if (mod->rst > mod->len || mod->xxo[mod->rst] >= mod->pat) {
		ord = ep;
	    } else {
		if (libxmp_get_sequence(ctx, mod->rst) == chain) {
	            ord = mod->rst;
		} else {
		    ord = ep;
	        }
	    }

	    pat = mod->xxo[ord];
	    if (has_marker && pat == S3M_END) {
		break;
	    }
	}

	pat = mod->xxo[ord];
	info = &m->xxo_info[ord];

	/* Allow more complex order reuse only in main sequence */
	if (ep != 0 && p->sequence_control[ord] != 0xff) {
	    /* Currently to detect the end of the sequence, the player needs the
	     * end to be a real position and row, so skip invalid and S3M_SKIP.
	     * "amazonas-dynomite mix.it" by Skaven has a sequence (9) where an
	     * S3M_END repeats into an S3M_SKIP.
	     *
	     * Two sequences (7 and 8) in "alien incident - leohou2.s3m" by
	     * Purple Motion share the same S3M_END due to an off-by-one jump,
	     * so check S3M_END here too.
	     */
	    if (pat >= mod->pat) {
		if (has_marker && pat == S3M_END) {
			ord = mod->len;
		}
		continue;
	    }
	    break;
	}
	p->sequence_control[ord] = chain;

	/* All invalid patterns skipped, only S3M_END aborts replay */
	if (pat >= mod->pat) {
	    if (has_marker && pat == S3M_END) {
		ord = mod->len;
	        continue;
	    }
	    continue;
	}

        if (break_row >= mod->xxp[pat]->rows) {
            break_row = 0;
        }

	/* Changing patterns may reset loop vars. */
	if (HAS_FLOW_MODE(FLOW_LOOP_PATTERN_RESET)) {
	    f.loop_start = -1;
	    f.loop_count = 0;
	    for (i = 0; i < mod->chn; i++) {
		f.loop[i].start = 0;
		f.loop[i].count = 0;
	    }
	}

        /* Loops can cross pattern boundaries, so check if we're not looping */
        if (m->scan_cnt[ord][break_row] && !inside_loop) {
            break;
        }

        /* Only update pattern information if we weren't here before. This also
         * means that we don't update pattern information if we're inside a loop,
         * otherwise a loop containing e.g. a global volume fade can make the
         * pattern start with the wrong volume. (fixes xyce-dans_la_rue.xm replay,
         * see https://github.com/libxmp/libxmp/issues/153 for more details).
         */
        if (info->time < 0) {
            info->gvl = gvl;
            info->bpm = bpm;
            info->speed = speed;
	    /* TODO: double ord_data::time */
	    time_calc = time + m->time_factor * frame_count * base_time / bpm;
            info->time = time_calc > (double)INT_MAX ? INT_MAX : (int)time_calc;
#ifndef LIBXMP_CORE_PLAYER
            info->st26_speed = st26_speed;
#endif
        }

	if (info->start_row == 0 && ord != 0) {
	    if (ord == ep) {
		start_time = time + m->time_factor * frame_count * base_time / bpm;
	    }

	    info->start_row = break_row;
	}

	/* Get tracks in advance to speed up the event parsing loop. */
	for (chn = 0; chn < mod->chn; chn++) {
		tracks[chn] = mod->xxt[TRACK_NUM(pat, chn)];
	}

	last_row = mod->xxp[pat]->rows;
	for (row = break_row, break_row = 0; row < last_row; row++, row_count++, row_count_total++) {
	    /* Prevent crashes caused by large softmixer frames */
	    if (bpm < XMP_MIN_BPM) {
	        bpm = XMP_MIN_BPM;
	    }

	    /* Date: Sat, 8 Sep 2007 04:01:06 +0200
	     * Reported by Zbigniew Luszpinski <zbiggy@o2.pl>
	     * The scan routine falls into infinite looping and doesn't let
	     * xmp play jos-dr4k.xm.
	     * Claudio's workaround: we'll break infinite loops here.
	     *
	     * Date: Oct 27, 2007 8:05 PM
	     * From: Adric Riedel <adric.riedel@gmail.com>
	     * Jesper Kyd: Global Trash 3.mod (the 'Hardwired' theme) only
	     * plays the first 4:41 of what should be a 10 minute piece.
	     * (...) it dies at the end of position 2F
	     */

	    if (row_count_total > row_limit) {
		D_(D_CRIT "row_count_total = %d @ ord %d, pat %d, row %d; ending scan", row_count_total, ord, pat, row);
		goto end_module;
	    }

	    if (!f.loop_active_num && !line_jump && m->scan_cnt[ord][row]) {
		row_count--;
		goto end_module;
	    }
	    m->scan_cnt[ord][row]++;
	    orders_since_last_valid = 0;
	    any_valid = 1;

	    /* If the scan count for this row overflows, break.
	     * A scan count of 0 will help break this loop in playback (storlek_11.it).
	     */
	    if (!m->scan_cnt[ord][row]) {
		goto end_module;
	    }

	    pdelay = 0;
	    line_jump = 0;

	    for (chn = 0; chn < mod->chn; chn++) {
		if (row >= tracks[chn]->rows)
		    continue;

		/* event = &EVENT(mod->xxo[ord], chn, row); */
		event = &tracks[chn]->event[row];

		f1 = event->fxt;
		p1 = event->fxp;
		f2 = event->f2t;
		p2 = event->f2p;

		if (f1 == 0 && f2 == 0) {
			continue;
		}

		if (f1 == FX_GLOBALVOL || f2 == FX_GLOBALVOL) {
		    gvl = (f1 == FX_GLOBALVOL) ? p1 : p2;
		    gvl = gvl > m->gvolbase ? m->gvolbase : gvl < 0 ? 0 : gvl;
		}

		/* Process fine global volume slide */
		if (f1 == FX_GVOL_SLIDE || f2 == FX_GVOL_SLIDE) {
		    int h, l;
		    parm = (f1 == FX_GVOL_SLIDE) ? p1 : p2;

		process_gvol:
                    if (parm) {
			gvol_memory = parm;
                        h = MSN(parm);
                        l = LSN(parm);

		        if (HAS_QUIRK(QUIRK_FINEFX)) {
                            if (l == 0xf && h != 0) {
				gvl += h;
			    } else if (h == 0xf && l != 0) {
				gvl -= l;
			    } else {
		                if (m->quirk & QUIRK_VSALL) {
                                    gvl += (h - l) * speed;
				} else {
                                    gvl += (h - l) * (speed - 1);
				}
			    }
			} else {
		            if (m->quirk & QUIRK_VSALL) {
                                gvl += (h - l) * speed;
			    } else {
                                gvl += (h - l) * (speed - 1);
			    }
			}
		    } else {
                        if ((parm = gvol_memory) != 0)
			    goto process_gvol;
		    }
		}

		/* Some formats can have two FX_SPEED effects, and both need
		 * to be checked. Slot 2 is currently handled first. */
		for (i = 0; i < 2; i++) {
		    parm = i ? p1 : p2;
		    if ((i ? f1 : f2) != FX_SPEED || parm == 0)
			continue;
		    frame_count += row_count * speed;
		    row_count = 0;
		    if (HAS_QUIRK(QUIRK_NOBPM) || p->flags & XMP_FLAGS_VBLANK || parm < 0x20) {
			speed = parm;
#ifndef LIBXMP_CORE_PLAYER
			st26_speed = 0;
#endif
		    } else {
			time += m->time_factor * frame_count * base_time / bpm;
			frame_count = 0;
			bpm = parm;
		    }
		}

#ifndef LIBXMP_CORE_PLAYER
		if (f1 == FX_SPEED_CP) {
		    f1 = FX_S3M_SPEED;
		}
		if (f2 == FX_SPEED_CP) {
		    f2 = FX_S3M_SPEED;
		}

		/* ST2.6 speed processing */

		if (f1 == FX_ICE_SPEED && p1) {
		    if (LSN(p1)) {
		        st26_speed = (MSN(p1) << 8) | LSN(p1);
		    } else {
			st26_speed = MSN(p1);
		    }
		}

		/* FAR tempo processing */

		if (f1 == FX_FAR_TEMPO || f1 == FX_FAR_F_TEMPO) {
			int far_speed, far_bpm, fine_change = 0;
			if (f1 == FX_FAR_TEMPO) {
				if (MSN(p1)) {
					far_tempo_mode = MSN(p1) - 1;
				} else {
					far_tempo_coarse = LSN(p1);
				}
			}
			if (f1 == FX_FAR_F_TEMPO) {
				if (MSN(p1)) {
					far_tempo_fine += MSN(p1);
					fine_change = MSN(p1);
				} else if (LSN(p1)) {
					far_tempo_fine -= LSN(p1);
					fine_change = -LSN(p1);
				} else {
					far_tempo_fine = 0;
				}
			}
			if (libxmp_far_translate_tempo(far_tempo_mode, fine_change,
			    far_tempo_coarse, &far_tempo_fine, &far_speed, &far_bpm) == 0) {
				frame_count += row_count * speed;
				row_count = 0;
				time += m->time_factor * frame_count * base_time / bpm;
				frame_count = 0;
				speed = far_speed;
				bpm = far_bpm;
			}
		}

		/* ULT tempo processing */

		if (f1 == FX_ULT_TEMPO || f2 == FX_ULT_TEMPO) {
		    int parm2 = 0;
		    parm = 0;
		    if (f2 == FX_ULT_TEMPO) {
			if (p2 == 0) {
				parm = 6;
				parm2 = 125;
			} else if (p2 < 0x30) {
				parm = p2;
			} else {
				parm2 = p2;
			}
		    }
		    if (f1 == FX_ULT_TEMPO) {
			if (p1 == 0) {
				parm = 6;
				parm2 = 125;
			} else if (p1 < 0x30) {
				parm = p1;
			} else {
				parm2 = p1;
			}
		    }
		    frame_count += row_count * speed;
		    row_count = 0;
		    if (parm > 0) {
			speed = parm;
			st26_speed = 0;
		    }
		    if (parm2 > 0) {
			time += m->time_factor * frame_count * base_time / bpm;
			frame_count = 0;
			bpm = parm2;
		    }
		}
#endif

		if ((f1 == FX_S3M_SPEED && p1) || (f2 == FX_S3M_SPEED && p2)) {
		    parm = (f1 == FX_S3M_SPEED) ? p1 : p2;
		    if (parm > 0) {
		        frame_count += row_count * speed;
		        row_count  = 0;
		        speed = parm;
#ifndef LIBXMP_CORE_PLAYER
		        st26_speed = 0;
#endif
		    }
		}

		if ((f1 == FX_S3M_BPM && p1) || (f2 == FX_S3M_BPM && p2)) {
		    parm = (f1 == FX_S3M_BPM) ? p1 : p2;
		    if (parm >= XMP_MIN_BPM) {
			frame_count += row_count * speed;
			row_count = 0;
			time += m->time_factor * frame_count * base_time / bpm;
			frame_count = 0;
			bpm = parm;
		    }
		}

#ifndef LIBXMP_CORE_DISABLE_IT
		if ((f1 == FX_IT_BPM && p1) || (f2 == FX_IT_BPM && p2)) {
		    parm = (f1 == FX_IT_BPM) ? p1 : p2;
		    frame_count += row_count * speed;
		    row_count = 0;
		    time += m->time_factor * frame_count * base_time / bpm;
		    frame_count = 0;

		    if (MSN(parm) == 0) {
		        time += m->time_factor * base_time / bpm;
			for (i = 1; i < speed; i++) {
			    bpm -= LSN(parm);
			    if (bpm < 0x20)
				bpm = 0x20;
		            time += m->time_factor * base_time / bpm;
			}

			/* remove one row at final bpm */
			time -= m->time_factor * speed * base_time / bpm;

		    } else if (MSN(parm) == 1) {
		        time += m->time_factor * base_time / bpm;
			for (i = 1; i < speed; i++) {
			    bpm += LSN(parm);
			    if (bpm > 0xff)
				bpm = 0xff;
		            time += m->time_factor * base_time / bpm;
			}

			/* remove one row at final bpm */
			time -= m->time_factor * speed * base_time / bpm;

		    } else {
			bpm = parm;
		    }
		}

		if (f1 == FX_IT_ROWDELAY) {
			/* Don't allow the scan count for this row to overflow here. */
			int x = m->scan_cnt[ord][row] + (p1 & 0x0f);
			m->scan_cnt[ord][row] = MIN(x, 255);
			frame_count += (p1 & 0x0f) * speed;
		}

		/* IT break is not applied if a lower channel looped (2.00+).
		 * (Labyrinth of Zeux ZX_11.it "Raceway"). */
		if (f1 == FX_IT_BREAK && f.loop_dest < 0) {
		    break_row = p1;
		    last_row = 0;
		}
#endif

		if (f1 == FX_JUMP || f2 == FX_JUMP) {
		    ord2 = (f1 == FX_JUMP) ? p1 : p2;
		    break_row = 0;
		    last_row = 0;

		    /* prevent infinite loop, see OpenMPT PatLoop-Various.xm */
		    inside_loop = 0;
		}

		if (f1 == FX_BREAK || f2 == FX_BREAK) {
		    parm = (f1 == FX_BREAK) ? p1 : p2;
		    break_row = 10 * MSN(parm) + LSN(parm);
		    last_row = 0;
		}

#ifndef LIBXMP_CORE_PLAYER
		/* Archimedes line jump */
		if (f1 == FX_LINE_JUMP || f2 == FX_LINE_JUMP) {
		    /* Don't set order if preceded by jump or break. */
		    if (last_row > 0)
			ord2 = ord;
		    parm = (f1 == FX_LINE_JUMP) ? p1 : p2;
		    break_row = parm;
		    last_row = 0;
		    line_jump = 1;
		}
#endif

		if (f1 == FX_EXTENDED || f2 == FX_EXTENDED) {
		    parm = (f1 == FX_EXTENDED) ? p1 : p2;

		    if ((parm >> 4) == EX_PATT_DELAY) {
			if (m->read_event_type != READ_EVENT_ST3 || !pdelay) {
			    pdelay = parm & 0x0f;
                        }
		    }

		    if ((parm >> 4) == EX_PATTERN_LOOP) {
			/* QUIRK_FT2BUGS may set break_row */
			f.jumpline = break_row;
			libxmp_process_pattern_loop(ctx, &f, chn, row, LSN(parm));
			break_row = f.jumpline;

			/* Attempt to detect the inside of a loop.
			 * TODO: this won't detect all cases. */
			if (LSN(parm) > 0 && f.loop_dest < 0) {
			    inside_loop = 0;
			} else if (LSN(parm) == 0) {
			    inside_loop = 1;
			}
		    }
		}
	    }

	    if (pdelay > 0) {
		frame_count += pdelay * speed;
	    }

	    f.loop_param = -1;
	    if (f.loop_dest >= 0) {
		/* -1 as it will be incremented immediately by the loop. */
		row = f.loop_dest - 1;
		f.loop_dest = -1;
	    }

#ifndef LIBXMP_CORE_PLAYER
	    if (st26_speed) {
	        frame_count += row_count * speed;
	        row_count  = 0;
		if (st26_speed & 0x10000) {
			speed = (st26_speed & 0xff00) >> 8;
		} else {
			speed = st26_speed & 0xff;
		}
		st26_speed ^= 0x10000;
	    }
#endif
	}

	if (break_row && pdelay) {
	    break_row++;
	}

	if (ord2 >= 0) {
	    ord = ord2 - 1;
	    ord2 = -1;
	}

	frame_count += row_count * speed;
	row_count_total = 0;
	row_count = 0;
    }
    row = break_row;

end_module:

    /* Sanity check */
    {
        if (!any_valid) {
	    return -1;
	}
        pat = mod->xxo[ord];
        if (pat >= mod->pat || row >= mod->xxp[pat]->rows) {
            row = 0;
        }
    }

    p->scan[chain].num = m->scan_cnt[ord][row];
    p->scan[chain].row = row;
    p->scan[chain].ord = ord;

    time -= start_time;
    frame_count += row_count * speed;

    /* TODO: double scan_data::time */
    time_calc = time + m->time_factor * frame_count * base_time / bpm;
    return time_calc > (double)INT_MAX ? INT_MAX : (int)time_calc;
}

static void reset_scan_data(struct context_data *ctx)
{
	int i;
	for (i = 0; i < XMP_MAX_MOD_LENGTH; i++) {
		ctx->m.xxo_info[i].time = -1;
	}
	memset(ctx->p.sequence_control, 0xff, XMP_MAX_MOD_LENGTH);
}

#ifndef LIBXMP_CORE_PLAYER
static void compare_vblank_scan(struct context_data *ctx)
{
	/* Calculate both CIA and VBlank time for certain long MODs
	 * and pick the more likely (i.e. shorter) one. The same logic
	 * works regardless of the initial mode selected--either way,
	 * the wrong timing mode usually makes modules MUCH longer. */
	struct player_data *p = &ctx->p;
	struct module_data *m = &ctx->m;
	struct ord_data *info_backup;
	struct scan_data scan_backup;
	unsigned char ctrl_backup[256];

	if ((info_backup = (struct ord_data *)malloc(sizeof(m->xxo_info))) != NULL) {
		/* Back up the current info to avoid a third scan. */
		scan_backup = p->scan[0];
		memcpy(info_backup, m->xxo_info, sizeof(m->xxo_info));
		memcpy(ctrl_backup, p->sequence_control,
			sizeof(p->sequence_control));

		reset_scan_data(ctx);

		m->quirk ^= QUIRK_NOBPM;
		p->scan[0].time = scan_module(ctx, 0, 0);

		D_(D_INFO "%-6s %dms", !HAS_QUIRK(QUIRK_NOBPM)?"VBlank":"CIA", scan_backup.time);
		D_(D_INFO "%-6s %dms",  HAS_QUIRK(QUIRK_NOBPM)?"VBlank":"CIA", p->scan[0].time);

		if (p->scan[0].time >= scan_backup.time) {
			m->quirk ^= QUIRK_NOBPM;
			p->scan[0] = scan_backup;
			memcpy(m->xxo_info, info_backup, sizeof(m->xxo_info));
			memcpy(p->sequence_control, ctrl_backup,
				sizeof(p->sequence_control));
		}

		free(info_backup);
	}
}
#endif

int libxmp_get_sequence(struct context_data *ctx, int ord)
{
	struct player_data *p = &ctx->p;
	return p->sequence_control[ord];
}

int libxmp_scan_sequences(struct context_data *ctx)
{
	struct player_data *p = &ctx->p;
	struct module_data *m = &ctx->m;
	struct xmp_module *mod = &m->mod;
	struct scan_data *s;
	int i, ep;
	int seq;
	unsigned char temp_ep[XMP_MAX_MOD_LENGTH];

	s = (struct scan_data *) realloc(p->scan, MAX(1, mod->len) * sizeof(struct scan_data));
	if (!s) {
		D_(D_CRIT "failed to allocate scan data");
		return -1;
	}
	p->scan = s;

	/* Initialize order data to prevent overwrite when a position is used
	 * multiple times at different starting points (see janosik.xm).
	 */
	reset_scan_data(ctx);

	ep = 0;
	temp_ep[0] = 0;
	p->scan[0].time = scan_module(ctx, ep, 0);
	seq = 1;

#ifndef LIBXMP_CORE_PLAYER
	if (m->compare_vblank && !(p->flags & XMP_FLAGS_VBLANK) &&
	    p->scan[0].time >= VBLANK_TIME_THRESHOLD) {
		compare_vblank_scan(ctx);
	}
#endif

	if (p->scan[0].time < 0) {
		D_(D_CRIT "scan was not able to find any valid orders");
		return -1;
	}

	while (1) {
		/* Scan song starting at given entry point */
		/* Check if any patterns left */
		for (i = 0; i < mod->len; i++) {
			if (p->sequence_control[i] == 0xff) {
				break;
			}
		}
		if (i != mod->len && seq < MAX_SEQUENCES) {
			/* New entry point */
			ep = i;
			temp_ep[seq] = ep;
			p->scan[seq].time = scan_module(ctx, ep, seq);
			if (p->scan[seq].time > 0)
				seq++;
		} else {
			break;
		}
	}

	if (seq < mod->len) {
		s = (struct scan_data *) realloc(p->scan, seq * sizeof(struct scan_data));
		if (s != NULL) {
			p->scan = s;
		}
	}
	m->num_sequences = seq;

	/* Now place entry points in the public accessible array */
	for (i = 0; i < m->num_sequences; i++) {
		m->seq_data[i].entry_point = temp_ep[i];
		m->seq_data[i].duration = p->scan[i].time;
	}

	return 0;
}
